New Structural Approach for Determination of Effective Thermoelastic Modules of Discrete Composite Layers

The rule of mixture (ROM) for the thermoelastic properties of layered composite materials is important if we apply the effective single-layer model (ELSM), and their refinement is an actual problem. In contrast to the classical linear plate theory (CLPT), real through-the-thickness strain distributions for thick and moderately thick plates may significantly deviate from the linear ones, which is demonstrated for the typical stacks of layers within the framework of 3-D linear elasticity theory using the finite-element method (FEM). If the linear strain distribution is interpreted as a statistical regression model, then the concept of ESLM may be proposed for laminated plates in a wider range of the length-to-thickness ratio. The idea of the offered new ROM within the structural approach, taking into account material properties, reinforcement orientation, thickness, and discrete layers position in a stack, is based on the separate classification of strain and stress contributions of stiffer or more flexible layers for each in-plane (normal and shear) component. Following a statistical approach, hypotheses regarding to through-the-thickness strain and stress distributions are formulated. The averaging technique is shown in detail for all in-plane strains and stresses. Similar to the CLPT, a matrix constitutive relation between forces-moments and averaged strains-curvatures are obtained. The stiffness matrices of the laminated composite are calculated using both arithmetic (direct) and geometric (inverse) averaging rules. In the future, verification, improvement, and implementation of the approach are planned.